Evidence of phonon-charge-density-waves coupling in ErTe$_3$

TL;DR

This study uses Raman spectroscopy to reveal how phonons interact with charge density waves in ErTe$_3$, showing mode coupling in the normal phase and new modes in the distorted state.

Contribution

It provides experimental evidence of phonon-charge-density-wave coupling in ErTe$_3$, linking vibrational properties to charge density wave phenomena.

Findings

All Raman modes in the normal phase are coupled to charge density waves.

New vibrational modes appear in the distorted state.

Raman active modes are assigned based on diperiodic symmetry analysis.

Abstract

The vibrational properties of ErTe$_3$ were investigated using Raman spectroscopy and analyzed on the basis of peculiarities of the RTe$_3$ crystal structure. Four Raman active modes for the undistorted structure, predicted by factor-group analysis, are experimentally observed and assigned according to diperiodic symmetry of the ErTe$_3$ layer. By analyzing temperature dependence of the Raman mode energy and intensity we have provided the clear evidence that all Raman modes, active in the normal phase, are coupled to the charge density waves. In addition, new modes have been observed in the distorted state.